Animal and cell culture models of pulmonary fibrosis are being developed. X-radiation of the one lung in the rabbit (3000 to 6000 R) results in increases in the rates of collagen synthesis per cell and accumulation of collagen. Methods have been developed to quantitate the rates of collagen synthesis in lung cells in culture and to quantitate the relative amounts of types of collagen being synthesized. These techniques are being combined with in vitro analogs of tissue injury to evaluate the modulation of inflammatory and immune mediators on the control of collagen accumulation in the lung.